The normal way we set about trying to extend our lives is by striving to add more years to them – usually by eating more couscous and broccoli, going to bed early and running in the rain. But this approach may turn out to be quixotic, not only because Death can’t reliably be warded off with kale, but at a deeper level, because the best way to lengthen a life is not by attempting to stick more years on to its tail.​One of the most basic facts about time is that, even though we insist on measuring it as if it were an objective unit, it doesn’t, in all conditions, feel as if it were moving at the same pace. Five minutes can feel like an hour; ten hours can feel like five minutes. A decade may pass like two years; two years may acquire the weight of half a century. And so on.

In other words, our subjective experience of time bears precious little relation to the way we like to measure it on a clock. Time moves more or less slowly according to the vagaries of the human mind: it may fly or it may drag. It may evaporate into airy nothing or achieve enduring density.​If the goal is to have a longer life, whatever the dieticians may urge, it seems like the priority should not be to add raw increments of time but to ensure that whatever years remain feel appropriately substantial. The aim should be to densify time rather than to try to extract one or two more years from the fickle grip of Death. ​Why then does time have such different speeds, moving at certain points bewilderingly fast, at others with intricate moderation? The clue is to be found childhood. The first ten years almost invariably feel longer than any other decade we have on earth. The teens are a little faster but still crawl. Yet by our 40s, time will have started to trot; and by our 60s, it will be unfolding at a bewildering gallop.

​The difference in pace is not mysterious: it has to do with novelty. The more our days are filled with new, unpredictable and challenging experiences, the longer they will feel. And, conversely, the more one day is exactly like another, the faster it will pass by in an evanescent blur. Childhood ends up feeling so long because it is the cauldron of novelty; because its most ordinary days are packed with extraordinary discoveries and sensations: these can be as apparently minor yet as significant as the first time we explore the zip on a cardigan or hold our nose under water, the first time we look at the sun through the cotton of a beach towel or dig our fingers into the putty holding a window in its frame. Dense as it is with stimuli, the first decade might as well be a thousand years long.

​By middle age, things can be counted upon to have grown a lot more familiar. We may have flown around the world a few times. We no longer get excited by the idea of eating a pineapple, owning a car or flipping a lightswitch. We know about relationships, earning money and telling others what do. And as a result, time runs away from us without mercy.

One solution often suggested at this point is that we should put all our efforts into discovering fresh sources of novelty. We can’t just continue to live our small predictable and therefore ‘swift’ lives in a single narrow domain; we need to become explorers and adventurers. We must go to Machu Picchu or Angkor Wat, Astana or Montevideo, we need to find a way to swim with dolphins or order a thirteen course meal at a world-famous restaurant in downtown Lima. That will finally slow down the cruel gallop of time.

But this is to labour under an unfair, expensive and ultimately impractical notion of novelty. We may by middle age certainly have seen a great many things in our neighborhoods, but we are – fortunately for us – unlikely to have properly noticed most of them. We have probably taken a few cursory glances at the miracles of existence that lie to hand and assumed, quite unjustly, that we know all there is to know about them. We’ve imagined we understand the city we live in, the people we interact with and, more or less, the point of it all.

But of course we have barely scratched the surface. We have grown bored of a world we haven’t begun to study properly. And that, among other things, is why time is racing by.

The pioneers at making life feel longer in the way that counts are not dieticians, but artists. At its best, art is a tool that reminds us of how little we have fathomed and noticed. It re-introduces us to ordinary things and reopens our eyes to a latent beauty and interest in precisely those areas we had ceased to bother with. It helps us to recover some of the manic sensitivity we had as newborns. Here is Cezanne, looking closely at apples, as if he had never seen one before and nudging us to do likewise:

Here is Van Gogh, mesmerised by some oranges:

​Here is Albrecht Durer, looking – as only children usually do – very closely at a clod of earth:

We don’t need to make art in order to learn the most valuable lesson of artists, which is about noticing properly, living with our eyes open – and thereby, along the way, savouring time. Without any intention to create something that could be put in a gallery, we could – as part of a goal of living more deliberately – take a walk in an unfamiliar part of town, ask an old friend about a side of their life we’d never dared to probe at, lie on our back in the garden and look up at the stars or hold our partner in a way we never tried before. It takes a rabid lack of imagination to think we have to go to Machu Picchu to find something new.​ In Fyodor Dostoevsky’s novel The Idiot, a prisoner has suddenly been condemned to death and been told he has only a few minutes left to live. ‘What if I were not to die!,’ he exclaims. ‘What if life were given back to me – what infinity!… I’d turn a whole minute into an age…’ Faced with losing his life, the poor wretch recognises that every minute could be turned into aeons of time, with sufficient imagination and appreciation.

It is sensible enough to try to live longer lives. But we are working with a false notion of what long really means. We might live to be a thousand years old and still complain that it had all rushed by too fast. We should be aiming to lead lives that feel long because we have managed to imbue them with the right sort of open-hearted appreciation and unsnobbish receptivity, the kind that five-year-olds know naturally how to bring to bear. We need to pause and look at one another’s faces, study the evening sky, wonder at the eddies and colours of the river and dare to ask the kind of questions that open our souls. We don’t need to add years; we need to densify the time we have left by ensuring that every day is lived consciously – and we can do this via a manoeuvre as simple as it is momentous: by starting to notice all that we have as yet only seen.